pkg 1.17 and later: What's the recommended way to fix problems due to removed keywords?

Hello,

Using FreeBSD 13.0-RELEASE-p4, I am stuck trying to get apache24 from
ports built and installed.
There are two problems:

1. complaints about the correct setting of DISABLE_VULNERABILITIES option:
the first build stopped, telling me I'd have to set
'DISABLE_VULNERABILITIES=yes'.
The next build complained that the variable would have to be set to a
"boolean" value.
What would be a "correct" value if 'yes' isn't accepted?
Anyway, the build proceeded.

2. Using the command line "make -DBATCH -DDISABLE_VULNERABILITIES
install" the build part seems to work.
But, after the build pkg-static complained that it does not know
keywords "preunexec" and "postexec" and aborted.
Searching the web led me to the porters handbook:
https://docs.freebsd.org/en/books/porters-handbook/plist/#plist-keywords
(see section 8.6.13.2.)
Searching further, I read that a lot of keywords have been removed
with pkg 1.17. (See
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=257384#c1 )
However, the porters' handbook doesn't mention the keywords as being deprecated.

My questions:
a) what could be the reason why pkg does not install Apache24, instead
putting out these complaints? Have more keywords been removed than the
porters' handbook states as "deprecated"?
b) what would be the correct way to get installed apache24, and maybe
other ports that fail the same way?

Thank you all for your help!
Stefan